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This invention relates to thermal garments. In particular, this invention relates to a thermal insulation garment that provides the wearer, thermal protection from low temperature aquatic and terrestrial environments, utilizing the body""s exhaled respiratory gases.
There are numerous extreme low temperature environments that human beings are exposed to requiring the use of thermal insulating garments and systems. Arctic scuba divers are exposed to temperatures as low as 0 degrees Celsius, the freezing temperature of water. Researchers living in Antarctica, and at high altitudes can be exposed to temperatures as low is minus 50 degrees Celsius. Future dwellers on the surface of Mars would be exposed to temperatures as low as minus 128 degrees Celsius. Each of these environments requires the use of a thermal insulating system in order for a human being to survive.
The function of any low temperature protection thermal garment is to retain the body""s heat in order to provide the wearer a comfortable operating environment. Body heat loss is minimized by thermal garments in their various ways of minimizing heat transfer from the body to the cooler external environment. The garments are typically made of multiple layers of thermoprotective materials. Some of these materials are: Lycra, polypropylene, foam neoprene, fleece, compressed neoprene, vulcanized rubber, etc. There is usually an inner layer that wicks away moisture and sometimes this layer is also designed to reflect radiant heat back to the body. The middle layer is usually the main insulating layer that traps a fluid, air or water, between it and the body, enhancing overall insulation.
Thermal protection is essential for the aquatic environment of scuba divers. Water exposure temperatures range from a comfortable high of 30xc2x0 C. (86xc2x0 F.) to low of just above freezing, 0xc2x0 C. (32xc2x0 F.) in fresh water and xe2x88x921.9xc2x0 C. (28.58xc2x0 F.) in seawater. The human body cools rapidly in water, as water conducts heat out of the body 20 times faster than standard atmospheric air. Therefore it is vital to provide thermal exposure protection over the duration of the dive. Dive times range from 30 minutes for typical open water dives to essentially unlimited dive times for commercial divers using a surface air supply. Typical thermal insulation garments focus on reducing the body""s overall thermal conductivity to the water, with different technologies for arctic, standard, and tropical water environments. Heat loss underwater is primarily via conduction and convection to the water; radiation heat loss is minimal in comparison. Several solutions to the problem of keeping warm in extreme cold conditions are practiced in the commercial diving industry. Dry-suits are often used to provide a diver with thermal protection in water from 30 to 0 degrees Celsius. Dry-suits utilize a layer of unheated air between the diver""s skin and water, as the means of insulation. The limitation of the dry-suit is that the air is supplied from the diver""s air supply, which is at the ambient water temperature. The dry-suit exposes the skin to chilled air, which the body must then warm, resulting in continual body heat loss. Therefore the dry-suit provides an extremely limited exposure times, as there is no heating mechanism employed. Another thermal insulation system used in the commercial diving industry is the xe2x80x98hot-water-machinexe2x80x99. The xe2x80x98hot-water-machinexe2x80x99 is used to pump heated water from the surface into the suit of divers at depth. There are some detractors to this method such as skin irritation from dirty water, scalding of the divers skin, the need for an external power source, and limited diving range. The main limitation of current aquatic thermal insulation garments is that they are passive systems that merely slow down the cooling process. Consequently, a diver can only remain in the water for a limited amount of time. Current diving thermal insulation systems that employ an active heating mechanism require the use of an external power source and connection to the surface.
Some of the coldest regions on Earth are the polar zones of the Arctic a nd Antarctic. The climates of polar lands vary greatly depending on their latitude, proximity of the sea, elevation, and topography. The lowest extreme surface temperatures in the winter are between xe2x88x9254xc2x0 and xe2x88x9246xc2x0 C. (xe2x88x9265xc2x0 and xe2x88x9250xc2x0 F.). Precipitation and winds reduce the effective temperatures for human exposure in the arctic, as they facilitate convection between the body and external environment. Terrestrial cold-weather garments utilize trapped air as their means of insulation. Down-like layers or equally low-density synthetic materials provide a layer of air insulation, effectively reducing the wearer""s overall thermal conductivity as well as providing water resistance and wind protection. Such garments are cumbersome and their effective use is limited to extremely short exposure times as there is no heating mechanism employed, only an insulating lower to slow down heat loss. Additionally there is no mechanism to prevent heat loss from the lung due to the natural breathing cycle.
Although there have been no humans on Mars to date, there is still much work being performed on developing thermal insulation technologies to protect humans from the severe temperature extremes and well as the low-pressure environment they will be exposed to. The average temperature for the Martian surface is xe2x88x9253xc2x0 C. (xe2x88x9264xc2x0 F.), with temperature extremes of xe2x88x92128xc2x0 C.(xe2x88x92199xc2x0 F.) on a winter night up to 36.8xc2x0 C. (98.3xc2x0 F.) on a warm summer day. Atmospheric pressure on Mars averages 0.01 atm or 10 mb. As a consequence of the low atmospheric pressure, radiation is the main mode of heat transfer. During high surface winds, however, heat loss due to atmospheric convection is increased. Currently derivatives of spacesuits or pressurized heated modules are the methods under consideration for thermal protection on the surface. The limitations of spacesuits are the extreme cost and lack of mobility. Pressurized heated modules are also expensive and inefficient.
Thus, in accordance with this background an improved low temperature thermal insulating garment is proposed that will extend the duration of exposure and the wearer""s mobility by providing an exhalant based, self-sustaining, means of body temperature maintenance.
The present invention provides thermal control and maintenance for low temperature environments.
An object of the invention is to provide thermal protection for low temperature terrestrial environments as low as negative 50 degrees Celsius.
Another object of the invention is to provide thermal protection for low temperature diving environment as low as zero degrees Celsius.
Another object of the invention is to provide thermal protection under pressurized space or surface suits for use on the surface of mars.
Another object of the invention is to provide extended dive times exceeding that of current diving thermal insulation garments and systems.
Another object of the invention is to provide unlimited exposure times for low temperature terrestrial environments.
Another object of the invention is to provide the wearer with increased mobility over current thermal insulating systems for low temperature environments.
Another object of the invention is to provide low-energy requirement and selfsustaining body temperature maintenance.
Another object of the invention is to use the body""s expired respiratory gases and natural thermal production capabilities to insulate and maintain a comfortable skin temperature.
Another object of the invention is to promote an even distribution of heated air over the entire body surface, including the head, hands, and feet, in a rapid manner.
Another object of the invention is to reduce heat loss during the breathing cycle.
Another object of the invention is to use the body""s expired gasses to warm incoming air.
Another object of the invention is to reduce water vapor lost from the lungs.
Another. object of the invention is to prevent the deleterious effects of excess water vapor inside the garment.
Another object of the invention is to provide a waterproof exterior.
Still another object of the invention is to mate with an external pressurized air supply.
This invention consists of a close fitting garment within which continuously flows the wearer""s heated exhalant (expired gasses). The garment recycles the heat in exhaled gas by using it to establish a warm microclimate around the wearer. A mouthpiece with a check-valve shunts exhaled air to the garment. The inner surface of the mouthpiece is textured to promote warming and humidification of the inhaled air. In order to facilitate heat flow within the garment, a network of flexible channels and bladders carry the heated gasses from the mouthpiece outlet over the entire body surface. This provides a constantly re-supplied warm insulation layer, substantially increasing exposure time to the low temperature environment. The garment also reduces radiant heat loss with a reflective layer and provides further conductive insulation with an external waterproofing-neoprene layer. Lastly, inhaled air is directed through the network of channels. in the garment to heat it before entering the mouthpiece, reducing heat loss due to the natural breathing cycle. All of these aspects combine to provide substantial improvements over current low temperature thermal garments with regards to extended exposure times, high mobility, and self-sufficiency.